using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var (m, order) = Coins(n, a);
        WriteLine(m);
        WriteLine(order);
    }
    static (long m, string order) Coins(int n, int[] a)
    {
        if (n == 2)
        {
            return (Coin(a[0], a[1]), "1 2");
        }
        if (n == 3)
        {
            var min = long.MaxValue;
            var minorder = "";
            {
                var m = Coin(Coin(a[0], a[1]), a[2]);
                if (min > m)
                {
                    min = m;
                    minorder = "1 2\n1 2";
                }
            }
            {
                var m = Coin(Coin(a[0], a[2]), a[1]);
                if (min > m)
                {
                    min = m;
                    minorder = "1 3\n1 2";
                }
            }
            {
                var m = Coin(Coin(a[1], a[2]), a[0]);
                if (min > m)
                {
                    min = m;
                    minorder = "2 3\n1 2";
                }
            }
            return (min, minorder);
        }
        var order = new System.Text.StringBuilder();
        order.Append($"1 2\n1 2\n{n-3} {n-2}");
        for (var i = n - 3; i >= 2; --i)
        {
            order.Append($"\n1 {i}");
        }
        return (0, order.ToString());
    }
    static long Coin(long a, long b)
    {
        checked {
            if (a == 0 || b == 0) return 0;
            if (GCD(a, b) > 1) return 0;
            return (a - 1) * (b - 1);
        }
    }
    static long GCD(long a, long b)
    {
        if (a < b) return GCD(b, a);
        if (a % b == 0) return b;
        return GCD(b, a % b);
    }
}